Scan-to-QC: Quality Control of Prefabricated Structural Systems Using Point Clouds

This study explores the use of point clouds for both representation and genetic morphogenesis of complex geometry. The accurate representation of existing objects of complex curved geometry, which are subsequently geometrically modified by evolutionary morphogenetic processes, is analysed. To this end, as a method of representation and generation of complex geometries, a point-based genetic algorithm and the use of large unstructured point clouds are proposed. A study of convergence and diversity of the implemented algorithm is detailed, as well as a comparison with the Coyote optimisation algorithm in terms of representation error demonstrating its efficiency. Some commonly used three-dimensional formats in architecture, such as NURBS and polygon meshes, are analysed, and compared against point clouds. This study also includes an evaluation regarding whether the use of point clouds is a more suitable format for realistic representation, rationalisation and genetic morphogenesis.

3D point cloud-based place recognition has gotten more attention since 3D LiDAR sensors are widely used for robotic applications and autonomous driving. Most of the existing deep point cloud-based methods take a few regular number points or image-like formats as inputs which are inability to make full use of point clouds' geometric information. This paper proposes a novel place recognition approach that is flexible and effective to handle diverse numbers of 3D LiDAR point clouds in large-scale environments. The approach is composed of feature extraction and a global descriptor encoding. The feature extraction consumes the 3D LiDAR point cloud with KPConv that can extract features efficiently and flexibly. Before the global descriptor encoding, a transformer module is employed to aggregate the contextual information that exploits the relationship of all features. The NetVLAD layer encodes the features into a global descriptor for recognizing a similar place rapidly. The proposed approach is evaluated on the KITTI odometry dataset, which demonstrates the validity of the proposed approach.

Visual SLAM systems are well established and the use of point clouds as a data source is also increasing. There are also higher demands on the registration of point cloud data. Traditional ICP algorithms are prone to fall into the problem of local optimal solutions in 3D point cloud data registration. To this end, the ICP algorithm was further improved by optimizing the objective function and reducing the density of the point cloud, with the aim of improving the accuracy and speed of point cloud registration.

The article presents the method of identifying the shorelines for natural watercourses located in agricultural and forest areas in accordance with applicable law. In the process of developing methods for identification and verification of the actual course of watercourses, data from the cadastral map was used in the form of a vector drawing of borders and a database with border points in ZRD, BPP attributes, metadata and point clouds. The identification of the course of a watercourse on shrubbery and wooded areas as well as on-screen vectorization of the shoreline is cumbersome, and in some cases even impossible. In connection with the above, it has been proposed to use a point cloud and vertical sections prepared on their basis that run perpendicular to the edge of the watercourse. On their basis, the course of the shoreline was recognized in accordance with the definition contained in the Act on Water Law. Pursuant to § 9 para. 3a, beginning of the regulation that the land occupied by the natural seepage constitutes a separate cadastral plot within the boundary line, the suggested procedures for verifying the boundaries of watercourses can be used to update the land and building register databases. The identification of the boundaries of registered parcels made on the principles described in the publication may precede the activities of accepting the boundaries to the division of real estate. On the other hand, the course of the identified, in the mode of § 82a, the regulation the boundaries of registration plots constituting natural watercourses can be shown in the land and building register on the terms specified in art. 24 sec. 2b point 2) geodesy law, in order to replace data inconsistent with the actual state and applicable technical standards, respectively, data consistent with the actual state and applicable technical standards (§ 45 section 1 point 1 of the Regulation).

3D Modeling Approach of Building Construction based on Point Cloud Data Using LiDAR Byeongjun Oh, Minju Kim, Chanwoo Lee, Hunhee Cho and Kyung-In Kang Pages 906-912 (2019 Proceedings of the 36th ISARC, Banff, Canada, ISBN 978-952-69524-0-6, ISSN 2413-5844) Abstract: LiDAR (Light Detection and Ranging) emerges as a mapping technology that provides fast, accurate, and reliable data with geometric representation of construction facilities. The technology has received high recognition especially since the importance of digital transformation in construction projects has been emphasized. However, the current state of 3D technologies including LiDAR encounters difficulty in recognizing and extracting accurate information on the as-built status of the buildings and construction sites. As a preliminary study for the development of a 3D architectural geometric representation of building and environment, this paper proposes a 3D modeling approach based on point cloud data obtained by LiDAR technology. This paper suggests a novel method for data acquisition on as-built status of construction sites and buildings during construction-operation phases. Furthermore, a field test has been performed for visualizing and modeling of the indoors of a residential house. The results of this paper are expected to inaugurate adaptation of LiDAR technology during the as-built process, and further implementation of digital technology after construction phase in construction projects. Keywords: LiDAR; 3D modeling; building construction; digital transformation; point cloud data DOI: https://doi.org/10.22260/ISARC2019/0121 Download fulltext Download BibTex Download Endnote (RIS) TeX Import to Mendeley

3D quality inspection is widely applied in many industrial fields including mould design, automotive and blade manufacturing, etc. A commonly used method is to obtain the point cloud of the inspected object and make a comparison between the point cloud and the corresponding CAD model or template. Thus, it is important to align the point cloud with the template first and foremost. Moreover, for the purpose of automatization of quality inspection, this alignment process is expected to be completed without manual interference. In this paper, we propose to combine the particle swarm optimization (PSO) with iterative closest point (ICP) algorithm to achieve the automated point cloud alignment. The combination of the two algorithms can achieve a balance between the alignment speed and accuracy, and avoid the local optimal caused by bad initial position of the point cloud.

Low efficiency and poor accuracy are caused by missing data in traditional 3D reconstruction methods. This study suggests a new 3D point cloud recognition technique for substation equipment based on 3D laser scanning point clouds, which combines the k-nearest neighbour (KNN) classification algorithm and particle swarm optimisation (PSO) algorithm, to address these issues. The particle swarm optimisation algorithm optimises the coefficient weights of each subspace feature. The k-nearest neighbour classification algorithm is then used to finish the classification. To confirm the superiority and accuracy of the suggested approach, the impact of the point cloud subspace’s size and loss rate on the recognition effect is examined experimentally and contrasted with the enhanced iterative nearest point algorithm. With an average recognition time of 0.19 seconds and a recognition accuracy of over 95\%, the experimental results demonstrate the method’s good performance in terms of efficiency and accuracy, opening up a wide range of potential applications.

The use of point clouds to digitally represent three-dimensional objects with both geometry and color attributes is rapidly increasing in several applications. Since storage and transmission of uncompressed point cloud data are often impractical, several lossy compression algorithms have been proposed, each exhibiting specific types of visual distortion. This creates a challenging environment for objective quality metrics, which might be effective only on a restricted number of distortion types and contexts. To evaluate the performance of the most recent objective quality metrics in predicting distortions as perceived by humans, a benchmarking study is conducted using subjective scores from observers examining models distorted with a conventional as well as a learning-based compression method, while rendering them on both a traditional flat monitor and an eye-sensing light field display. The results are then analyzed and conclusions are drawn on the correlation between recent state-of-the-art objective quality metrics and human perception on two different types of visualization devices.

3D point clouds, a new primitive representation for objects, are spreading among thousands of people through internet software. Thus, the privacy preserving problem of the 3D point cloud should be widely concerned by more and more people. To ensure the safe transmission and use of point cloud, two schemes of encryption have been proposed by using chaotic cat mapping in this paper. The two encryption schemes are tested by using various types of 3D point clouds. In addition, these proposed encryption algorithms are analyzed through key space, sensibility, statistical and encryption time analysis. These analysis results show that the two proposed schemes can resist the common existing cipher attacks and are effective encryption methods for 3D point cloud encryption. At the same time, the two promising encryption algorithms can guarantee the security of the 3D point cloud model transmitted on the Internet.

In this paper, we propose an algorithm for the registration of the GPS sensor and the stereo camera for vehicle localization within 3D dense point clouds. We adopt the particle swarm optimization algorithm to perform the sensor registration and the vehicle localization. The registration of the GPS sensor and the stereo camera is performed to increase the robustness of the vehicle localization algorithm. In the standard GPS-based vehicle localization, the algorithm is affected by noisy GPS signals in certain environmental conditions. We can address this problem through the sensor fusion or registration of the GPS and stereo camera. The sensors are registered by estimating the coordinate transformation matrix. Given the registration of the two sensors, we perform the point cloud-based vehicle localization. The vision-based localization is formulated as an optimization problem, where the “optimal” transformation matrix and corresponding virtual point cloud depth image is estimated. The transformation matrix, which is optimized, corresponds to the coordinate transformation between the stereo and point cloud coordinate systems. We validate the proposed algorithm with acquired datasets, and show that the algorithm robustly localizes the vehicle.

Voxel is one of the common structural representation of 3D point cloud. Due to the sparsity of point cloud generated by light detection and ranging (LiDAR), there is the extreme imbalance in the foreground and background voxels. It decreases the accuracy of 3D object detection, has the negative effect on intelligent driving safety. To overcome this problem, we present a saliency prediction based 3D object detector SP-Det in this article. Although foreground voxels have the sufficient feature of object, it is difficult to localize the foreground region from voxel space with the larger background region. We design an auxiliary learning task, saliency prediction (SP). It benefits 3D detector in identifying the foreground region. SP task uses label diffusion to alleviate the label imbalance. It reduces the learning difficulty of saliency in voxel and bird's eye view (BEV) spaces. After that, to strengthen feature interaction from the sparse foreground region, we design saliency fusion (SF) module to fuse the learning result in SP task. It utilizes voxel and BEV saliency maps as progressive attention to resist the redundant feature from background region. To aggregate more foreground feature inside 3D and BEV region of interest (RoI), we design hybrid grid maps based RoI pooling (Hybrid-RoI pooling). Experiments are conducted in STF dataset. The adverse weather enlarges the sparsity of LiDAR point cloud, increasing the difficulty of object detection. SP-Det identifies and leverages foreground region, and achieves the performance better than the current methods. Hence, we believe that SP-Det benefits to LiDAR based 3D scene understanding in the adverse weather.

Multidimensional particle swarm optimization-based unsupervised planar segmentation algorithm of unorganized point clouds

Multi-modal data fusion plays a critical role in enhancing the accuracy and robustness of perception systems for autonomous driving, especially for the detection of small objects. However, small object detection remains particularly challenging due to sparse LiDAR points and low-resolution image features, which often lead to missed or imprecise detections. Currently, many methods process LiDAR point clouds and visible-light camera images separately, and then fuse them in the detection head. However, these approaches often fail to fully exploit the advantages of multi-modal sensors and overlook the potential for enhancing the correlation between modalities before feature fusion. To address this, we propose a novel LiDAR-guided multi-modal fusion framework for object detection, called LGMMfusion. This framework leverages the depth information from LiDAR to guide the generation of image Bird's Eye View (BEV) features. Specifically, LGMMfusion promotes spatial interaction between point clouds and pixels before the fusion of LiDAR BEV and image BEV features, enabling the generation of higher-quality image BEV features. To better align image and LiDAR features, we incorporate a multi-head multi-scale self-attention mechanism and a multi-head adaptive cross-attention mechanism, using the prior depth information from point clouds to generate image BEV features that better match the spatial positions of LiDAR BEV features. Finally, the LiDAR BEV features and image BEV features are fused to provide enhanced features for the detection head. Experimental results show that LGMMfusion achieves 71.1% NDS and 67.3% mAP on the nuScenes validation set, while also improving the detection of small objects and enhancing the detection accuracy of most objects.

Accurate detection of objects in perception system is a basic task for autonomous vehicles to operate reliably. The current mainstream paradigms for perception and prediction are able to decompose into three sequential subtasks: detection, tracking and prediction. Much of the previous works focus on one of these subtasks and internal relationship between the various subtasks are therefore ignored. In this work we propose an end-to-end model that is able to jointly carry out 3D detection and motion prediction in the context of autonomous vehicles, which can benefit from joint optimization of two tasks. Considering computational consumption and memory cost, our approach utilizes 2D convolutions across space over a bird's eye view (BEV) representation of the 3D world, not 3D convolutions which require more inference time for a single point cloud. In this paper, the key model is the sequential multi-frame point clouds channels based on BEV, which can help perform object detection and learn temporal information at the same time. Experiments on nuScenes dataset show that the proposed network achieves state-of-the-art results, and the trade-off between accuracy and efficiency of two tasks are obtained. Additionally, we validate the effectiveness of our models through the ablation studies. Specifically, by sharing network, parameters and detection results we can perform two tasks within 32 FPS.

BEV-CFKT: A LiDAR-camera cross-modality-interaction fusion and knowledge transfer framework with transformer for BEV 3D object detection